Mods:
Mariculture V.MARICULTURE-1.7.10-1.2.3D and
Thermal Expansion V.THERMALEXPANSION-[1.7.10]4.0.0B5-13

Explenation:
Okey it's very simple, When you put a Empty bucket into a Fluid Transposer with Lava. When it's finished filling the bucket, instead of outputing a Bucket of Lava it seems to be replaced by Mariculture and it outputs a Nether droplet (Lava Droplet) instead. I think this might be a problem with the Nether Droplet replacing the Vanilla Lava Buckets output.

No. This is to do with the fact that the fluid registry will not allow null containers. It automatically adds buckets as the output. Imma have to add a dried up droplet or something stupid like that.

Useless droplets are added.